1. Field of the Invention
The present invention relates to a developing member to be incorporated into an apparatus adopting an electrophotographic mode such as a copying machine, a printer, or a receiving equipment of a facsimile, a process cartridge, and an electrophotographic image forming apparatus.
2. Description of the Related Art
A developing member to be used in an electrophotographic apparatus is often provided with an electro-conductive elastic layer containing a silicone rubber in order that stress to be applied to toner may be alleviated and a nip width between the member and an electrophotographic photosensitive member may be secured. In addition, a surface of such elastic layer is often provided with a surface layer for, for example, controlling charging of the toner and controlling a conveyance amount of the toner.
By the way, a recent electrophotographic apparatus has started to be required to have higher image quality and higher durability. Accordingly, its developing member has also started to be required to have higher durability. In some cases, however, a charging member provided with an elastic layer containing a silicone rubber, the layer being made electro-conductive by incorporating an electro-conductive agent such as carbon black, has shown a variation in electrical resistance owing to its long-term use, and the variation has affected the quality of an electrophotographic image.
Meanwhile, Japanese Patent Application Laid-Open No. 2001-158856 discloses a semiconductive silicone rubber composition whose electrical resistance hardly varies owing even to, for example, an environmental change such as a temperature or humidity change, a change in blending amount of carbon black, or application of a high voltage. Specifically, the Japanese Patent Application Laid-Open No. 2001-158856 discloses a semiconductive silicone rubber composition whose electrical resistance hardly varies, the composition being obtained by incorporating, into a silicone rubber, thermal black having a specific nitrogen adsorption specific surface area, a specific DBP oil absorption amount, and a specific average particle diameter obtained by thermally decomposing a natural gas. In addition, the Japanese Patent Application Laid-Open No. 2001-158856 discloses an application of such semiconductive silicone rubber composition to an electro-conductive roller.